Metathesis catalysts have been previously described by for example, U.S. Pat. Nos. 5,312,940, 5,342,909, 5,728,917, 5,750,815, 5,710,298, and 5,831,108 and PCT Publications WO 97/20865 and WO 97/29135 which are all incorporated herein by reference. These publications describe well-defined single component ruthenium or osmium catalysts that possess several advantageous properties. For example, these catalysts are tolerant to a variety of functional groups and generally are more active than previously known metathesis catalysts. In an unexpected and surprising result, the inclusion of an N-heterocyclic carbene ligand in these metal-carbene complexes had been found to dramatically improve the already advantageous properties of these catalysts. The preparation of well-defined ruthenium alkylidene complexes bearing N-heterocyclic carbene ligands such as 1,3-dimesitylimidazol-2-ylidene and 4,5-dihydroimidazol-2-ylidene, have led to other catalysts which are highly active in metathesis reactions, including ring-closing metathesis (RCM), acyclic diene metathesis (ADMET), cross metathesis (CM), and ring-opening metathesis polymerization (ROMP). These catalysts show increased thermal stability and similar tolerance to oxygen and moisture when compared to their parent bisphosphine complexes, Cl2(PCy3)2Ruxe2x95x90CHR. However, since all synthetic routes to the N-heterocyclic carbene complexes proceed through transformation of a ruthenium bisphosphine carbene, a direct route through readily available starting materials is still needed.
The invention relates to preparing and measuring the metathesis activity of ruthenium vinylidene and cumulene complexes bearing an N-heterocyclic ligand. The catalysts used in the present invention are of the general formula: 
wherein
M is ruthenium or osmium;
X and X1 are the same of different and are each independently an anionic ligand;
NHC is any N-heterocyclic carbene ligand;
L1 is any neutral electron donor ligand; and,
R, R1 and R2 are each independently hydrogen or a substituent selected from the group consisting of C1-C20 alkyl, C2-C20 alkenyl, C2-C20 alkynyl, aryl, C1-C20 carboxylate, C1-C20 alkoxy, C2-C20 alkenyloxy, C2-C20 alkynyloxy, aryloxy, C2-C20 alkoxycarbonyl, C1-C20 alkylthio, C1-C20 alkylsulfonyl and C1-C20 alkylsulfinyl. Optionally, each of the R, R1, or R2 substituent group may be substituted with one or more moieties selected from the group consisting of C1-C10 alkyl, C1-C10 alkoxy, and aryl which in turn may each be further substituted with one or more groups selected from a halogen, a C1-C5 alkyl, C1-C5 alkoxy, and phenyl. Moreover, any of the catalyst ligands may further include one or more functional groups. Examples of suitable functional groups include but are not limited to: hydroxyl, thiol, thioether, ketone, aldehyde, ester, ether, amine, imine, amide, nitro, carboxylic acid, disulfide, carbonate, isocyanate, carbodiimide, carboalkoxy, carbamate, and halogen. Examples of N-heterocyclic carbene ligands include: 
wherein R6, R7, R8, R9, R10 and R11 are each independently hydrogen or a substituent selected from the group consisting of C1-C20 alkyl, C2-C20 alkenyl, C2xe2x80x94C20 alkynyl, aryl, C1-C20 carboxylate, C1-C20 alkoxy, C2-C20 alkenyloxy, C2-C20 alkynyloxy, aryloxy, C2-C20 alkoxycarbonyl, C1-C20 alkylthio, C1-C20 alkylsulfonyl and C1-C20 alkylsulfinyl. Optionally, each of the R, R1, R2, R6, R7, R8, R9, R10 and R11 substituent group may be substituted with one or more moieties selected from the group consisting of C1-C10 alkyl, C1-C10 alkoxy, and aryl which in turn may each be further substituted with one or more groups selected from a halogen, a C1-C5 alkyl, C1-C5 alkoxy, and phenyl. Moreover, any of the catalyst ligands may further include one or more functional groups. Examples of suitable functional groups include but are not limited to: hydroxyl, thiol, thioether, ketone, aldehyde, ester, ether, amine, imine, amide, nitro, carboxylic acid, disulfide, carbonate, isocyanate, carbodiimide, carboalkoxy, carbamate, and halogen.
The invention relates to preparing and measuring the metathesis activity of various ruthenium vinylidene and cumulene complexes bearing N-heterocyclic carbene ligands. In particular, the invention provides for the preparation of novel ruthenium and osmium vinylidene and cumulene complexes bearing at least one N-heterocyclic carbene ligand and measures their activity in ring-opening metathesis polymerization reactions, acyclic diene metathesis reactions, ring-closing metathesis reactions, and cross-metathesis reactions. The invention further relates to the generation of these catalysts in situ with air-stable components. The terms xe2x80x9ccatalystxe2x80x9d and xe2x80x9ccomplexxe2x80x9d herein are used interchangeably.
Unmodified ruthenium and osmium carbene complexes have been described in U.S. Pat. Nos. 5,312,940, 5,342,909, 5,728,917, 5,750,815, and 5,710,298, all of which are incorporated herein by reference. The ruthenium and osmium carbene complexes disclosed in these patents all possess metal centers that are formally in the +2 oxidation state, have an electron count of 16, and are penta-coordinated. These catalysts are of the general formula 
wherein:
M is ruthenium or osmium;
X and X1 are each independently any anionic ligand;
L and L1 are each independently any neutral electron donor ligand;
R and R1 are each independently hydrogen or a substituent selected from the group consisting of C1-C20 alkyl, C2-C20 alkenyl, C2-C20 alkynyl, aryl, C1-C20 carboxylate, C1-C20 alkoxy, C2-C20 alkenyloxy, C2-C20 alkynyloxy, aryloxy, C2-C20 alkoxycarbonyl, C1-C20 alkylthio, C1-C20 alkylsulfonyl and C1-C20 alkylsulfinyl. Optionally, each of the R or R1 substituent group may be substituted with one or more moieties selected from the group consisting of C1-C10 alkyl, C1-C10 alkoxy, and aryl which in turn may each be further substituted with one or more groups selected from a halogen, a C1-C5 alkyl, C1-C5 alkoxy, and phenyl. Moreover, any of the catalyst ligands may further include one or more functional groups. Examples of suitable functional groups include but are not limited to: hydroxyl, thiol, thioether, ketone, aldehyde, ester, ether, amine, imine, amide, nitro, carboxylic acid, disulfide, carbonate, isocyanate, carbodiimide, carboalkoxy, carbamate, and halogen.
More recently, and as described in PCT Publication Nos. WO 99/51344, WO 00/58322, and WO 00/71554, the contents of each of which are incorporated herein by reference, catalysts bearing an N-heterocyclic ligand have shown increased thermal stability. These catalysts are as described above except that L is an unsubstituted or substituted n-heterocyclic carbene ligand of the general formula: 
wherein:
R6, R7, R8, R9, R10 and R11 are each independently hydrogen or a substituent selected from the group consisting of C1-C20 alkyl, C2-C20 alkenyl, C2-C20 alkynyl, aryl, C1-C20 carboxylate, C1-C20 alkoxy, C2-C20 alkenyloxy, C2-C20 alkynyloxy, aryloxy, C2-C20 alkoxycarbonyl, C1-C20 alkylthio, C1-C20 alkylsulfonyl and C1-C20 alkylsulfinyl. Optionally, each of the R, R1R6, R7, R8, R9, R10 and R11 substituent group may be substituted with one or more moieties selected from the group consisting of C1-C10 alkyl, C1-C10 alkoxy, and aryl which in turn may each be further substituted with one or more groups selected from a halogen, a C1-C5 alkyl, C1-C5 alkoxy, and phenyl. Moreover, any of the catalyst ligands may further include one or more functional groups. Examples of suitable functional groups include but are not limited to: hydroxyl, thiol, thioether, ketone, aldehyde, ester, ether, amine, imine, amide, nitro, carboxylic acid, disulfide, carbonate, isocyanate, carbodiimide, carboalkoxy, carbamate, and halogen. The inclusion of an NHC ligand to the ruthenium or osmium catalysts has been found to dramatically improve the properties of these complexes.
In preferred embodiments of the inventive catalysts, the R substituent is hydrogen and the R1 substituent is selected from the group consisting of C1-C20 alkyl, C2-C20 alkenyl, and aryl. In even more preferred embodiments, the R1 substituent is phenyl or vinyl, optionally substituted with one or more moieties selected from the group consisting of C1-C5 alkyl, C1-C5 alkoxy, phenyl, and a functional group. In especially preferred embodiments, R1 is phenyl or vinyl substituted with one or more moieties selected from the group consisting of chloride, bromide, iodide, fluoride, xe2x80x94NO2, xe2x80x94NMe2, methyl, methoxy and phenyl. In the most preferred embodiments, the R1 substituent is phenyl or xe2x80x94Cxe2x95x90C(CH3)2.
In preferred embodiments of the inventive catalysts, L1 is selected from the group consisting of phosphine, sulfonated phosphine, phosphite, phosphinite, phosphonite, arsine, stibine, ether, amine, amide, imine, sulfoxide, carboxyl, nitrosyl, pyridine, and thioether. In more preferred embodiments, L1 is a phosphine of the formula PR3R4R5, where R3, R4, and R5 are each independently aryl or C1-C10 alkyl, particularly primary alkyl, secondary alkyl or cycloalkyl. In the most preferred embodiments, L1 is each selected from the group consisting of xe2x80x94P(cyclohexyl)3, xe2x80x94P(cyclopentyl)3, xe2x80x94P(isopropyl)3, and xe2x80x94P(phenyl)3.
In preferred embodiments of the inventive catalysts, X and X1 are each independently hydrogen, halide, or one of the following groups: C1-C20 alkyl, aryl, C1-C20 alkoxide, aryloxide, C3-C20 alkyldiketonate, aryldiketonate, C1-C20 carboxylate, arylsulfonate, C1-C20 alkylsulfonate, C1-C20 alkylthio, C1-C20 alkylsulfonyl, or C1-C20 alkylsulfinyl. Optionally, X and X1 may be substituted with one or more moieties selected from the group consisting of C1-C10 alkyl, C1-C10 alkoxy, and aryl which in turn may each be further substituted with one or more groups selected from halogen, C1-C5 alkyl, C1-C5 alkoxy, and phenyl. In more preferred embodiments, X and X1 are halide, benzoate, C1-C5 carboxylate, C1-C5 alkyl, phenoxy, C1-C5 alkoxy, C1-C5 alkylthio, aryl, and C1-C5 alkyl sulfonate. In even more preferred embodiments, X and X1 are each halide, CF3CO2, CH3CO2, CFH2CO2, (CH3)3CO, (CF3)2(CH3)CO, (CF3)(CH3)2CO, PhO, MeO, EtO, tosylate, mesylate, or trifluoromethanesulfonate. In the most preferred embodiments, X and X1 are each chloride.
In preferred embodiments of the inventive catalysts, R6 and R7 are each independently hydrogen, phenyl, or together form a cycloalkyl or an aryl optionally substituted with one or more moieties selected from the group consisting of C1-C10 alkyl, C1-C10 alkoxy, aryl, and a functional group selected from the group consisting of hydroxyl, thiol, thioether, ketone, aldehyde, ester, ether, amine, imine, amide, nitro, carboxylic acid, disulfide, carbonate, isocyanate, carbodiimide, carboalkoxy, carbamate, and halogen; and R8 and R9 are each is independently C1-C10 alkyl or aryl optionally substituted with C1-C5 alkyl, C1-C5 alkoxy, aryl, and a functional group selected from the group consisting of hydroxyl, thiol, thioether, ketone, aldehyde, ester, ether, amine, imine, amide, nitro, carboxylic acid, disulfide, carbonate, isocyanate, carbodiimide, carboalkoxy, carbamate, and halogen.
In more preferred embodiments, R6 and R7 are both hydrogen or phenyl, or R6 and R7 together form a cycloalkyl group; and R8 and R9 are each either substituted or unsubstituted aryl. Without being bound by theory, it is believed that bulkier R8 and R9 groups result in catalysts with improved characteristics such as thermal stability. In especially preferred embodiments, R8 and R9 are the same and each is independently of the formula 
wherein:
R10, R11, and R12 are each independently hydrogen, C1-C10 alkyl, C1-C10 alkoxy, aryl, or a functional group selected from hydroxyl, thiol, thioether, ketone, aldehyde, ester, ether, amine, imine, amide, nitro, carboxylic acid, disulfide, carbonate, isocyanate, carbodiimide, carboalkoxy, carbamate, and halogen. In especially preferred embodiments, R10, R11, and R12 are each independently selected from the group consisting of hydrogen, methyl, ethyl, propyl, isopropyl, hydroxyl, and halogen. In the most preferred embodiments, R10, R11, and R12 are the same and are each methyl.
Examples of the most preferred embodiments of the complexes include: 
wherein Mes is 
(also known as xe2x80x9cmesityxe2x80x9d); ixe2x80x94Pr is isopropyl; and PCy3 is xe2x80x94P(cyclohexyl)3.
In all of the above carbene complexes, at least one of L1, X, X1, R and R1, may be linked to at least one other of L1, X, X1, R and R1 to form a bidentate or multidentate ligand array.
In Situ Generation of Catalysts
Ruthenium or osmium vinylidenes can be easily prepared from commercially available terminal alkynes and ruthenium sources. Unfortunately, such complexes have only been active in the ROMP of highly strained norbomenes. Without being bound by theory, it is believed that the mechanism of olefin metathesis is dissociative in ligand, i.e., phosphine or imidazolylidene, and it is well known that the latter ligands have relatively higher binding energies. The invention shows that carbenes bearing a mixed ligand set, i.e., one imidazolylidene and one phosphine, have pronounced activities.
The invention provides a process for the ring-closing metathesis of acyclic olefins using a ruthenium or osmium vinylidene or cumulene complex. Scheme 1 provides a general reaction scheme for this process: 
wherein M, X, X1, L1, NHC, R and R1 are as defined above. Again, a cumulene complex in accordance with the principles of the invention may also be used in the ring-closing metathesis reaction.
The vinylidenes and cumulenes may be prepared by simple ligand exchange as shown in Scheme 2: 
wherein M, X, X1, L1, R, R1 and R2 are as defined above.
For example, a ruthenium vinylidene possessing a mixed ligand system was prepared and investigated for RCM. Simple phosphine displacement of the known Cl2(PCy3) 2Ruxe2x95x90Cxe2x95x90CHtBu with bulky 1,3-dimesitylimidazol-2-ylidene (1) afforded Cl2(PCy3)(Imes)Ruxe2x95x90Cxe2x95x90CHtBu 8 in 85% yield as a brown solid. Complex 8 catalyzed the RCM of diethyl diallylmalonate in 86% yield (Table 1, entry 1a). Although the reaction rate was much slower than ruthenium alkylidenes, this was the first example of RCM catalyzed by a ruthenium vinylidene complex. By metathesis active catalyst, it is meant that the catalyst is in a low-coordination state, for example a tetracoordinated complex. Without being bound by theory, it is believed that the slow rate of reaction may result from slow initiation since the propagating species (methylidene) is identical to one produced by carbene complex Cl2 (PCy3)(Imes)Ruxe2x95x90CHPh 3.
Further, and without being bound by theory, it is believed that these results show ligand dissociation (i.e., phosphine) was necessary to increase catalytic activity. Previously, addition of phosphine sponges, such as copper salts or acid, has been used to facilitate RCM catalyzed by ruthenium carbenes. An alternative approach would involve the direct generation of the phosphine-free active species in situ, thus circumventing the need for adding additional reagents to remove phosphine. The general reaction scheme for generating the metathesis active species in situ begins with the generation of an NHC carbene from the NHC carbene salt as shown in Scheme 3:
The NHC carbene may also be generated using a xe2x80x9cprotectedxe2x80x9d NHC, for example, an s-IMES HCCl3 ligand. A discussion of protected NHC carbenes can be seen, for example, in U.S. application Nos. 60/288,680 filed May 3, 2001, and U.S. Provisional Application No. 60/309,806, the contents of each of which are incorporated herein by reference. The NHC carbene is then contacted with a ruthenium or osmium source, for example, a ruthenium chloride monomer or dimer, as shown in Scheme 4:
Monomers that provide a ruthenium or osmium source include ((C6H11)2HPRu(p-cymene)Cl2, (C6H11)3PRu(p-cymene)Cl2, (C6H11)3PRu(p-cymene)(tos)2, (C6H11)3PRu(p-cymene)BR2, (C6H11)3PRu(p-cymene)ClF, (C6H11)3PRu(C6H6)(tos)2, (C6H11)3PRu(CH3-C6H5)(tos)2, (C6H11)3PRu(C10H8)(tos)2,(I-C3H7)3PRup-cymene)Cl2, (CH3)3PRu(p-cymene)Cl2, (C6H11)3PRu(CH3xe2x80x94CN(C2H5-OH)(tos)2, (C6H11)3PRu(p-cymene)CH3xe2x80x94CN)2 (PF6)2(C6H11)3PRu(p-cymene)(CH3xe2x80x94CN)2(tos)2, (n-C4H9)3PRu(p-cymene)CH3xe2x80x94CN)2 (tos)2, (C6H11)3PRu(CH3CN)Cl2, (C6H11)3PRu(CH3xe2x80x94CN)2Cl2, (n-C4C4H9)3PRu(p-cymene)Cl2, (C6H11)3PRu(p-cymene)C2H5OH)2(BF4)2, (C6H11)3PRu(p-cymene)(C2H5OH)2(PF6)2, (i-C3H7)3POs(p-cymene)Cl2, (CH3)3POs(p-cymene)Cl2, (C6H5)3POs(p-cymene)Cl2, [(C8H11) 3P]3Ru(CH3xe2x80x94CN), (C5H9)3PRu(p-cymene)Cl2, (C6H11)3PRu(p-cymene)HCl, (C6H11) 3PRu[1, 2, 4, 5-(CH3)4(C6H2]Cl2, (C6H11)3PRu[1, 3, 5-(i-C3H7)3C6H3]Cl2, (C6H11)3PRu[(C6H9)xe2x80x94C6H5]Cl2, (C6H11)3POs(p-cymene)Cl2, (C6H5)3PRu(p-cymene)HCl, [(C6H11)3P]2Ru(CH3xe2x80x94CN)(tos)2, RuCl2(p-cymene)[(C6H11)2PCH2CH2P(C6H11)2], (C6H11)3PRu(p-cymene)(C2H5OH)BF4)2, (C6H11)3PRu(C6H6)(C2H5OH)2(tos)2, (C6H11)3PRu(i-C3H7xe2x80x94C6H5)(tos)2, (C6H11)3PRu(C6H6)(p-cymene)Br2, (C6H11)3PRu(biphenyl)(tos)2, (C6H11) 3PRu(anthracene)(tos)2, (2xe2x80x94CH3C6H4)3POs(p-cymene)Cl2, and (C6H11)3PRu(chrysene)(tos)2.
Any substituted or unsubstituted arene may be used, for example p-cymene or tolyls. Preferably, the arene is p-cymene.
Preferably, the NHC product from Scheme 4 is then contacted with an alkyne, preferably acetylene, to form the tetracoordinated metathesis active compound as shown in Scheme 5:
Other alkynes that may be used include ethyne, phenylethyne, 4-tert-butylphenylethyne, trimethylsilylethyne, and triethylsilylethyne. A more descriptive list of alkynes that may be used in accordance with the principles of the invention can be seen in U.S. Pat. No. 6,171,995, the contents of which are incorporated herein by reference.
Metathesis active cumulene complexes can be formed in situ in a similar manner as shown in Scheme 6: 
In all of the above schemes, NHC, M, X, X1, R, R1 and R2 are as defined above, and R3 is OH.
Preferred embodiments of the metathesis active catalysts are 
wherein Mes is 
(also known as xe2x80x9cmesitylxe2x80x9d); ixe2x80x94Pr is isopropyl; and PCy3 is xe2x80x94P(cyclohexyl)3.
Schemes 7-8 illustrate the generation of the preferred metathesis active vinylidene compound: 
For example, ruthenium vinylidenes can be conveniently prepared by adding 2 equivalents of phosphine and a terminal alkyne to [(p-cymene)RuCl2]2 (9). Table 1 shows the results of metathesis reactions using [(p-cymene)RuCl2]2/1Cl/tert-butyl acetylene where E=CO2Et unless otherwise indicated. The percent yield are the isolated yields and for entries 1a-f, the percent yield was determined using 1H NMR. In addition, for entries 1c-d, the percent yield represents the percent conversion. As shown in Table 1 (entry 1b), the combination of 2.5 mol % dimer 9, 5 mol % 1,3-dimesitylimidazol-2-ylidene (1), and 5 mol % of tert-butyl acetylene generated phosphine-free Cl2(Imes)Ruxe2x95x90Cxe2x95x90CHtBu in situ, which subsequently catalyzed the RCM of diethyl diallylmalonate affording the ring-closed product in 95% yield (80xc2x0 C., 12h, entry 1b). The reaction shown in entry 1b was performed with ligand 1 using toluene as a solvent.
The complex formed in situ displayed higher catalytic activity than Cl2(Imes)(PCy3)Ruxe2x95x90Cxe2x95x90CHtBu vinylidene (8) (86%, 65xc2x0 C., 24 h) which further suggests that a vinylidene possessing a low coordination number may be necessary for initiation.
The scope of the reagents needed to generate vinylidene catalysts in situ was investigated further. As expected, the absence of a ruthenium source or NHC ligand failed to provide any ring-closed product. While the absence of alkyne did provide ring-closed product, the reaction rates were slower (Table 1, entries 1c-d). The reactions shown in entries 1c and 1d also were performed with ligand 1 using toluene as a solvent; however, no tert-butyl acetylene was added in the reaction shown in entry 1d. Presumably, (P-cymene) (IMes)RuCl2, a known RCM catalyst precursor, is being generated in situ. However, the inclusion of alkyne resulted in substantially higher yields when the RCM reaction was performed in THF (entries 1e-f). The reactions shown in both entries 1e and 1f were performed with ligand 1 using THF as a solvent; however, no tert-butyl acetylene was added in the reaction shown in entry 1e. Thus, while the inventive process may be performed in the absence of a solvent, it is apparent from these control reactions that solvent plays an important role in the generation of a metathesis catalyst in situ.
Various solvents may be used with the inventive method. Examples of solvents that can be used in the polymerization reaction include organic, protic, or aqueous solvents, which are preferably inert under the polymerization conditions. Examples of such solvents include aromatic hydrocarbons, chlorinated hydrocarbons, ethers, aliphatic hydrocarbons, alcohols, water, or mixtures thereof. Preferred solvents include benzene, toluene, p-xylene, methylene chloride, dichloroethane, dichlorobenzene, chlorobenzene, tetrahydrofuran, diethylether, pentane, methanol, ethanol, water or mixtures thereof. More preferably, the solvent is hexane, benzene, toluene, p-xylene, methylene chloride, dichloroethane, dichlorobenzene, chlorobenzene, tetrahydrofuran, diethylether, pentane, methanol, ethanol, or mixtures thereof. Most preferably, the solvent is hexane. The solubility of the polymer formed in the polymerization reaction will depend on the choice of solvent and the molecular weight of the polymer obtained.
Although a number of imidazolylidenes are stable as their free carbene, an easier method would involve the generation of the free imidazolylidene carbene in situ from the appropriate salt and base. Such a method has been used to generate NHC ligand based vinyl alkylidene complexes, such as Cl2(PCy3)(s-IMES)Ruxe2x95x90CHxe2x80x94CHxe2x95x90C(CH3)2 (3) and Cl(PCy3)2RuH(H2) (4) as well as a palladium aryl amination catalyst. In hopes of extending this methodology to include metathesis reactions, the RCM of diethyl diallymalonate using [(p-cymene)RuCl2]2, NaOtBu, and each of the NHC salts shown below: 
under various conditions. Unfortunately, all RCM reactions with ligand 2X (X=BF4, Cl) failed to give cyclized product and may be related to the instability of the saturated imidazolylidene free carbene. Alternatively, the formation of the vinylidene precursor may be blocked due to deprotonation of the alkyne by base, although addition of alkyne as the final reagent still afforded only starting material. Similar results were obtained with 1Cl when the reactions were performed in either toluene or TEF. However, dramatically different results were obtained in hexanes. As shown in entry 1 g (Table 1), diethyl diallylmalonate was converted to the corresponding ring-closed product in 96% yield. The addition of alkyne was imperative as no product was observed in its absence (entry 1 h). Without being bound by theory, it is possible that a highly unstable and unsaturated alkoxide ruthenium complex is generated from the presence of NaOtBu. The combination of a low concentration of metal complex soluble in hexanes as well as the generation of a vinylidene complex from the addition of alkyne may produce a stable ruthenium vinylidene species resistant to decomposition (Scheme 10). 
As stated above, a variety of metathesis reactions were performed using this system (Table 1). Interestingly, in addition to RCM, the catalyst generated in situ was also effective in CM, ene-yne metathesis, ROMP, and ADMET. While reaction times were longer, sterically hindered olefins were cyclized in high in comparable yields to those obtained using complexes 3 and 4. As demonstrated in Table 1, the invention provides a process to generate a highly active metathesis catalyst, capable of ring-closing both trisubstituted and tetrasubstituted olefins, from inexpensive materials.
The metathesis active catalysts generated in situ are also useful in ring-opening metathesis polymerization (ROMP) reactions of strained or unstrained cyclic olefins. ROMP reactions follow the general scheme: 
wherein M, X, X1, L1, NHC, R and R1 are as defined above. Again, cumulene complexes in accordance with the principles of the invention may also be used.
The most preferred cyclic olefin monomer for use in ROMP reactions in accordance with the principles of the invention is substituted or unsubstituted dicyclopentadiene (DCPD). Various DCPD suppliers and purities may be used such as Lyondell 108 (94.6% purity), Veliscol UHP (99+% purity), B. F. Goodrich Ultrene(copyright) (97% and 99% purities), and Hitachi (99+% purity). Other preferred olefin monomers include other cyclopentadiene oligomers including trimers, tetramers, pentamers, and the like; cyclooctadiene (COD; DuPont); cyclooctene (COE, Alfa Aesar); cyclohexenylnorbomene (Shell); norbornene (Aldrich); norbornene dicarboxylic anhydride (nadic anhydride); norbornadiene (Elf Atochem); and substituted norbornenes including butyl norbornene, hexyl norbornene, octyl norbornene, decyl norbornene, and the like. Preferably, the olefinic moieties include mono-or disubstituted olefins and cycloolefins containing between 3 and 200 carbons. Most preferably, metathesis-active olefinic moieties include cyclic or multicyclic olefins, for example, cyclopropenes, cyclobutenes, cycloheptenes, cyclooctenes, [2.2.1]bicycloheptenes, [2.2.2]bicyclooctenes, benzocyclobutenes, cyclopentenes, cyclopentadiene oligomers including trimers, tetramers, pentamers, and the like; cyclohexenes. It is also understood that such compositions include frameworks in which one or more of the carbon atoms carry substituents derived from radical fragments including halogens, pseudohalogens, alkyl, aryl, acyl, carboxyl, alkoxy, alkyl- and arylthiolate, amino, amninoalkyl, and the like, or in which one or more carbon atoms have been replaced by, for example, silicon, oxygen, sulfur, nitrogen, phosphorus, antimony, or boron. For example, the olefin may be substituted with one or more groups such as thiol, thioether, ketone, aldehyde, ester, ether, amine, amide, nitro, carboxylic acid, disulfide, carbonate, isocyanate, phosphate, phosphite, sulfate, sulfite, sulfonyl, carbodiimide, carboalkoxy, carbamate, halogen, or pseudohalogen. Similarly, the olefin may be substituted with one or more groups such as C1-C20 alkyl, aryl, acyl, C1-C20 alkoxide, aryloxide, C3-C20 alkyldiketonate, aryldiketonate, C1-C20 carboxylate, arylsulfonate, C1-C20 alkylsulfonate, C1-C20 alkylthio, arylthio, C1-C20 alkylsulfonyl, and C1-C20 alkylsulfinyl, C1-C20 alkylphosphate, arylphosphate, wherein the moiety may be substituted or unsubstituted. Preferably, the olefin monomer is substituted or unsubstituted DCPD. In accordance with the principles of the invention, in a ROMP reaction, the polymer may be formed by a process comprising contacting the olefin monomer, preferably substituted or unsubstituted DCPD, with a ruthenium source such as dimer 9, and a source for the NHC carbene, such as a protected NHC or the NHC salt, preferably the s-IES salt.
These cyclic and acyclic olefin monomers may be used alone or mixed with each other in various combinations to adjust the properties of the olefin monomer composition. For example, mixtures of cyclopentadiene dimer and trimers offer a reduced melting point and yield cured olefin copolymers with increased mechanical strength and stiffness relative to pure poly-DCPD. As another example, incorporation of COD, norbornene, or alkyl norbornene co-monomers tend to yield cured olefin copolymers that are relatively soft and rubbery. The resulting polyolefin compositions formed from the metathesis reactions are amenable to thermosetting and are tolerant of additives, stabilizers, rate modifiers, hardness and/or toughness modifiers, fillers and fibers including, but not limited to, carbon, glass, aramid (e.g., Kevlar(copyright) and Twaron(copyright)), polyethylene (e.g., Spectra(copyright) and Dyneema(copyright)), polyparaphenylene benzobisoxazole (e.g., Zylon(copyright)), polybenzamidazole (PBI), and hybrids thereof as well as other polymer fibers.
The metathesis reactions may optionally include formulation auxiliaries. Known auxiliaries include antistatics, antioxidants (primary antioxidants, secondary antioxidants, or mixtures thereof), ceramics, light stabilizers, plasticizers, dyes, pigments, fillers, reinforcing fibers, lubricants, adhesion promoters, viscosity-increasing agents, and demolding enhancers. Illustrative examples of fillers for improving the optical physical, mechanical, and electrical properties include glass and quartz in the form of powders, beads, and fibers, metal and semi-metal oxides, carbonates (e.g. MgCO3, CaCO3), dolomite, metal sulfates (e.g. gypsum and barite), natural and synthetic silicates (e.g. zeolites, wollastonite, and feldspars), carbon fibers, and plastics fibers or powders.
The UV and oxidative resistance of the polyolefin compositions resulting from the metathesis reactions using the inventive carbene complex may be enhanced by the addition of various stabilizing additives such as primary antioxidants (e.g., sterically hindered phenols and the like), secondary antioxidants (e.g., organophosphites, thioesters, and the like), light stabilizers (e.g., hindered amine light stabilizers or HALS), and UV light absorbers (e.g., hydroxy benzophenone absorbers, hydroxyphenylbenzotriazole absorbers, and the like), as described in PCT Publication No. WO 00/46256, the contents of which are incorporated herein by reference.
Exemplary primary antioxidants include, for example, 4,4xe2x80x2-methylenebis (2,6-di-tertiary-butylphenol) (Ethanox 702(copyright); Albemarle Corporation), 1, 3, 5-trimethyl-2, 4, 6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene (Ethanox 330(copyright); Albermarle Corporation), octadecyl-3-(3xe2x80x2,5xe2x80x2-di-tert-butyl-4xe2x80x2-hydroxyphenyl) propionate (Irganox 1076(copyright); Ciba-Geigy), and pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate)(Irganox(copyright) 1010; Ciba-Geigy). Exemplary secondary antioxidants include tris(2,4-ditert-butylphenyl)phosphite (Irgafos(copyright) 168; Ciba-Geigy), 1:11 (3, 6, 9-trioxaudecyl)bis(dodecylthio)propionate (Wingstay(copyright) SN-1; Goodyear), and the like. Exemplary light stabilizers and absorbers include bis(1, 2, 2, 6, 6-pentamethyl-4-piperidinyl)-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate (Tinuvin(copyright) 144 HALS; Ciba-Geigy), 2-(2H-benzotriazol-2-yl)-4,6-ditertpentylphenol (Tinuvin(copyright) 328 absorber; Ciba-Geigy), 2,4-di-tert-butyl-6-(5-chlorobenzotriazol-2-yl)phenyl (Tinuvin(copyright) 327 absorber; Ciba-Geigy), 2-hydroxy-4-(octyloxy)benzophenone (Chimassorb(copyright) 81 absorber; Ciba-Geigy), and the like.
In addition, a suitable rate modifier such as, for example, triphenylphosphine (TPP), tricyclopentylphosphine, tricyclohexylphosphine, triisopropylphosphine, trialkylphosphites, triarylphosphites, mixed phosphites, pyridine, or other Lewis base, as described in U.S. Pat. No. 5,939,504 and U.S. application No. 09/130,586, the contents of each of which are herein incorporated by reference, may be added to the olefin monomer to retard or accelerate the rate of polymerization as required.
The resulting polyolefin compositions, and parts or articles of manufacture prepared therefrom, may be processed in a variety of ways including, for example, Reaction Injection Molding (RIM), Resin Transfer Molding (RTM) and vacuum-assisted variants such as VARTM (Vacuum-Assisted RMT) and SCRIMP (Seemann Composite Resin Infusion Molding Process), open casting, rotational molding, centrifugal casting, filament winding, and mechanical machining. These processing compositions are well known in the art. For example, when using a two-component system, the olefin monomer is contacted with the ruthenium source, such as dimer 9, and set aside as the first component. The second component comprises an olefin monomer and a source for the NHC carbene, such as the NHC salt or a protected NHC, such as a s-IMES-HCCl3. The reaction is initiated when the first component is contacted with the second component. Various molding and processing techniques are described, for example, in PCT Publication WO 97/20865, the disclosure of which is incorporated herein by reference.
Another aspect of the inventive process is conducting a ring-closing metathesis reaction or a ring-opening metathesis polymerization reaction in accordance with the principles of the invention without the use of a drybox or vacuum line or special Schlenk equipment using all air-stable starting materials. The solid components (commercially available) were weighed in air into a reaction flask. The atmosphere was purged with argon followed by the addition of reagent grade hexanes, tert-butyl acetylene and diethyl diallylmalonate. After 10 h at 80xc2x0 C., ring-closed product was obtained in 88% yield. The reaction rate and yield were comparable to when degassed solvents and drybox procedures were employed (96%, Table 1, entry 1 g).
The following examples are illustrative of the invention and it is understood that the invention is not limited to the disclosed embodiments but that various modifications and substitutions can be made thereto as would be apparent to those skilled in the art.